To answer the question of what drills undermine vertical leap ability, we need to first discuss what's needed for a good vertical jump. First, there's two types of vertical jumpers: standing and running. A standing vertical jump is when you are stationary on the ground and leap up with all your strength, useful in football and weightlifting. A running vertical jump is when you need to get high while you are running such as volleyball and basketball style vertical. Since you're question is about basketball, you want to focus on the following drills or activities:
Strength training can help you improve your relative strength, which is more important than your absolute strength for a running vertical--if you focus around the exercises that facilitate good jumping and don't get lost in the quest for heavier numbers. Rough guidelines would be to focus on things like these:
- Kettlebell swings (improves the power generation at the hip)
- Standing calf raises (improves your calf output, can help with tendons in the ankle as well)
- Squats need to be deep enough to hit the stretch reflex in your glutes
- Push press involves the hips as well as improving your shoulder strength. Overhead work will be more beneficial in general to a basketball player than bench pressing.
- Focus on more sets with low reps using moderate weight (example 6x3 @ 70% intensity): the goal is to build strength without too much bulk.
- Olympic weightlifting: builds hip power, and calf power through triple extension under load
This list is not complete, but it should give you an idea of things that can help a vertical and compliment basketball.
At the opposite end of the spectrum we want to avoid strength activities like this:
- General bodybuilding (increasing muscle mass for looks more than function)
- Power lifting (aiming for the heaviest squat/bench/deadlift you can)
- Anything where you are slowly grinding out reps through great effort
Those activities can benefit a football player, but basketball players have different demands on them.
The biggest factor with plyometric work is the type of plyo you employ, followed closely by the frequency. You want to focus on reactive strength, not standing strength
- Avoid standing box jumps (from a lower to higher platform)
- Perform depth jumps (from an 18" box to the floor and immediately jump when you land)
- Perform running jumps
- Perform quick jump shots (helps your game, and your reactive power at the same time--double win)
As to frequency, it might be best to have one day a week devoted to explosive work that gives you enough time to recover for a game later that week.
This is one where you may or may not agree with me. It turns out cardio work's interference with power output is exaggerated. In short, while there are mild acute affects (i.e. short term) in the long term, long slow cardio will make you a better athlete. My high school basketball coach always had us run a couple miles before practice even started. In retrospect it was a good thing.
- Some low intensity steady state (LISS) cardio work (running, cycling, etc) will help your recovery from difficult training and improve basic health factors. 20 minutes a day is plenty for this purpose.
- Sprints are great
- Suicides are also great, particularly since it also reinforces that stretch reflex in your calves as you change directions quickly
Skill Work is always important. The more you work at a skill the better you get at it. Your coach will have you running drills that are designed to bring the best out of you as a player. You'll always have to do what your coach says--or you won't be on a team and your vertical will be pointless. The coach should have his pulse on what makes his system work, and where his team needs more work.
The biggest challenge you'll have is to make sure anything you do outside of practice doesn't interfere with practice, or worse the game. If you play once a week, load the week so you do the bulk of your strength and plyometric work a day or two after your game and then taper off the closer to your next game (perhaps doing no outside work the day before a game). If you play twice a week, that's even more challenging but the same principles apply. You just might have one strength day and one plyo day a week.